The invention relates to an apparatus for manufacturing tubes made from thin-walled material, especially made from sheet metal, with a welding machine for longitudinal-seam welding and also with a clamping device, which has clamping jaws that are arranged on opposite sides of the tube blank and that can be pressed against the tube blank for holding a tubular, preformed blank in the welding position.
Apparatuses of the above-noted type are already known with a clamping device, whose clamping jaws each consist of a number of clamping elements, which are set at a distance from each other and which can be pressed against the tube blank for holding a tubular, preformed blank in the welding position. Because the gap between the tube blank sides to be welded to each other varies slightly in the region of each clamping element, the weld seam can rarely be produced with the desired accuracy and quality over the entire longitudinal extent, especially for contoured tubes.
Apparatuses with a clamping device that include pressure rollers arranged in pairs on opposite sides of the tube blank have also already been designed. Because the tube blank forms only a tangential contact with these pressure rollers, the pressure rollers can clamp the tube blank between themselves such that the sides of the tube blank to be welded to each other can contact each other uniformly in the welding region and a uniform weld seam is produced. However, such pressure rollers cannot be used in contoured tube blanks, which have outer diameters that vary over the longitudinal extent of the tube.